Macro vecc 

macro_rules! vecc {
    (@array ($($vecs:expr,)*)) => { ... };
    (@array ($($vecs:expr,)*) [$($elem:expr),+] $($rest:tt)*) => { ... };
    (@array ($($vecs:expr,)*) [$($elem:expr,)*] $($rest:tt)*) => { ... };
    (@array ($($vecs:expr,)*) [$elem:expr; $n:expr] $($rest:tt)*) => { ... };
    [] => { ... };
    [ $($tt:tt,)+ ] => { ... };
    [ $($tt:tt),+ ] => { ... };
}

Creates a vector of vector with vecc!, instead of repeating vec! multiple times.

Examaple: let v = vecc![[1, 2], [3, 4]];, it should equal to vec![vec![1, 2], vec![3, 4]]